Merge remote-tracking branch 'origin/main'

# Conflicts:
#	README.md

Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "m8db"
-version = "0.1.0"
+version = "1.3.0"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "m8db"
-version = "0.1.0"
+version = "1.3.0"
 edition = "2018"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

README.md

@@ -1,16 +1,23 @@
 # m8db
 
-Debugger and interpreter for the M8 pseudo-assembly language
+Debugger and interpreter for the M8 pseudo-assembly language. Inspired by `gdb` or `lldb`
 
 More infos: https://github.com/ah1m1/M8NI
 
+Usage: `$ ./m8db (filename)`
+
 
 # Instructions:  
 * `INC r`
 * `DEC r`
+* `JUMP label`
 * `JUMP line`
 * `STOP`
+* `IS_ZERO r label`
 * `IS_ZERO r line`
+* `.labelname`
 
-Where `r` is a register number and `line` is a line number.  
-`IS_ZERO` jumps to `line` if `r` is zero
+`# anything` is a comment
+
+Where `r` is a register number, `line` is a line number and `label` is a label name.  
+`IS_ZERO` jumps to `label` if `r` is zero

src/db.rs

@@ -1,197 +0,0 @@
-use crate::stmt::Stmt;
-use std::io::Write;
-
-#[derive(Debug, Clone)]
-struct Vm {
-    stmts: Vec<Stmt>,
-    pc: usize,
-    registers: Vec<usize>,
-    breakpoints: Vec<usize>,
-}
-
-#[derive(Debug, Copy, Clone)]
-enum VmState {
-    Run,
-    Break,
-    Stop,
-}
-
-impl Vm {
-    fn step(&mut self) -> VmState {
-        let pc = self.pc;
-        self.pc += 1;
-        match self.stmts[pc] {
-            Stmt::Inc(r) => self.registers[r] += 1,
-            Stmt::Dec(r) => self.registers[r] -= 1,
-            Stmt::IsZero(r, line) => {
-                if self.registers[r] == 0 {
-                    self.pc = line - 1;
-                }
-            }
-            Stmt::Jump(line) => self.pc = line - 1,
-            Stmt::Stop => return VmState::Stop,
-        }
-        if self.breakpoints.contains(&self.pc) {
-            VmState::Break
-        } else {
-            VmState::Run
-        }
-    }
-
-    fn run(&mut self) -> VmState {
-        loop {
-            match self.step() {
-                state @ (VmState::Break | VmState::Stop) => return state,
-                _ => {}
-            }
-        }
-    }
-}
-
-#[derive(Debug, Copy, Clone)]
-enum VmInstruction {
-    Step,
-    Run,
-    Break(usize),
-    Set(usize, usize),
-}
-
-pub fn run(stmts: Vec<Stmt>) {
-    let max_register_index = max_register(&stmts);
-    let mut vm = Vm {
-        stmts,
-        pc: 0,
-        registers: vec![0; max_register_index + 1],
-        breakpoints: vec![],
-    };
-
-    loop {
-        match debug_input(&mut vm) {
-            VmInstruction::Run => match vm.run() {
-                VmState::Stop => break,
-                VmState::Run => unreachable!(),
-                _ => {}
-            },
-            VmInstruction::Step => match vm.step() {
-                VmState::Stop => break,
-                _ => {}
-            },
-            VmInstruction::Break(line) => {
-                let position = vm.breakpoints.iter().position(|point| *point == line);
-                match position {
-                    None => vm.breakpoints.push(line),
-                    Some(pos) => {
-                        vm.breakpoints.remove(pos);
-                    }
-                }
-            }
-            VmInstruction::Set(r, value) => vm.registers[r] = value,
-        }
-    }
-}
-
-fn debug_input(vm: &Vm) -> VmInstruction {
-    loop {
-        let mut input_buf = String::new();
-        print!("(m8db) ");
-        std::io::stdout().flush().unwrap();
-        std::io::stdin().read_line(&mut input_buf).unwrap();
-        let input = input_buf.trim();
-        let mut iter = input.split_ascii_whitespace();
-        match iter.next() {
-            Some(str) => match str {
-                "r" | "register" => print_registers(vm),
-                "p" | "program" => print_program(vm),
-                "h" | "?" | "help" => print_help(),
-                "b" | "break" => match iter.next() {
-                    Some(num) => match num.parse() {
-                        Ok(num) => return VmInstruction::Break(num),
-                        Err(_) => println!("Invalid argument provided"),
-                    },
-                    None => print_breakpoints(vm),
-                },
-                "set" => match parse_set_command(&mut iter) {
-                    Some((reg, value)) => return VmInstruction::Set(reg, value),
-                    None => println!("Invalid arguments provided"),
-                },
-                "c" | "continue" => return VmInstruction::Run,
-                "s" | "step" => return VmInstruction::Step,
-                _ => {}
-            },
-            None => {}
-        }
-    }
-}
-
-fn parse_set_command<'a>(iter: &mut impl Iterator<Item = &'a str>) -> Option<(usize, usize)> {
-    let reg: usize = iter.next().and_then(|reg| reg.parse().ok())?;
-    let value: usize = iter.next().and_then(|value| value.parse().ok())?;
-    Some((reg, value))
-}
-
-fn max_register(stmts: &[Stmt]) -> usize {
-    stmts
-        .iter()
-        .map(|stmt| match stmt {
-            Stmt::Inc(r) => *r,
-            Stmt::Dec(r) => *r,
-            Stmt::IsZero(r, _) => *r,
-            Stmt::Jump(_) => 0,
-            Stmt::Stop => 0,
-        })
-        .max()
-        .unwrap_or(0)
-}
-
-fn print_registers(vm: &Vm) {
-    println!("Registers:");
-    for (i, r) in vm.registers.iter().enumerate() {
-        println!("{: >4} : {}", i, r);
-    }
-}
-
-fn print_program(vm: &Vm) {
-    use std::cmp::min;
-
-    println!("Program:");
-    let lower = if vm.pc > 5 { vm.pc - 5 } else { 0 };
-    let len = vm.stmts.len();
-    let higher = if len < 5 { len } else { min(vm.pc + 5, len) };
-
-    for i in lower..higher {
-        let stmt = vm.stmts[i];
-        if i == vm.pc {
-            println!("> {}  {}", i, stmt)
-        } else {
-            println!("{}  {}", i, stmt);
-        }
-    }
-}
-
-fn print_breakpoints(vm: &Vm) {
-    println!(
-        "Breakpoints:
-    {}
-    ",
-        vm.breakpoints
-            .iter()
-            .map(|p| p.to_string())
-            .collect::<Vec<String>>()
-            .join(", ")
-    );
-}
-
-fn print_help() {
-    println!(
-        "List of commands and their aliases:
-
-    step (s) -- Steps the program forward by one step
-    set <register> <value> -- Sets a register to a value
-    break <line> (b) -- Set a breakpoint to a line, use again to toggle
-    continue (c) -- Run the program until the next breakpoint
-    register (r) -- Shows the contents of the registers
-    program (p) -- Shows where the program currently is
-    help (h, ?) -- Shows this help page
-    "
-    );
-}

src/main.rs

@@ -1,15 +1,7 @@
-mod db;
-mod stmt;
+mod parse;
+mod run;
 
 fn main() {
-    let filename = match std::env::args().skip(1).next() {
-        Some(name) => name,
-        None => {
-            eprintln!("error: no file provided.\nUsage: <filename>");
-            return;
-        }
-    };
-
     println!(
         "m8db - M8 Debugger
 (C) Nilstrieb (https://github.com/Nilstrieb/m8db)
@@ -17,14 +9,5 @@ Type 'help' for help
     "
     );
 
-    let program = std::fs::read_to_string(filename).unwrap();
-    let statements = match stmt::parse(&program) {
-        Ok(stmts) => stmts,
-        Err(str) => {
-            eprintln!("{}", str);
-            return;
-        }
-    };
-    db::run(statements);
-    println!("Execution finished.");
+    run::start(std::env::args().nth(1));
 }

src/parse.rs

@@ -0,0 +1,257 @@
+use std::collections::HashMap;
+use std::fmt::Formatter;
+use std::num::ParseIntError;
+
+/// A span referencing the line where a statement came from. Starts at 0
+#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct Span(pub usize);
+
+impl Span {
+    pub fn line_number(&self) -> usize {
+        self.0 + 1
+    }
+}
+
+/// A line number, starts at 1
+#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct LineNumber(pub usize);
+
+impl LineNumber {
+    pub fn span(&self) -> Span {
+        Span(self.0 - 1)
+    }
+}
+
+/// An index into a `Vm` `Stmt`
+#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct StmtIdx(pub usize);
+
+/// A register index
+#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct Register(pub usize);
+
+#[derive(Debug, Copy, Clone)]
+pub enum Stmt {
+    Inc(Register),
+    Dec(Register),
+    IsZero(Register, StmtIdx),
+    Jump(StmtIdx),
+    Stop,
+}
+
+#[derive(Debug, Clone)]
+pub struct Code<'a> {
+    pub stmts: Vec<Stmt>,
+    /// Has the same length as `stmts`, points to line numbers where the instructions come from
+    pub span: Vec<Span>,
+    pub code_lines: Vec<&'a str>,
+    pub file_name: String,
+}
+
+#[derive(Debug, Clone)]
+enum IrStmt<'a> {
+    Inc(Register),
+    Dec(Register),
+    IsZeroLabel(Register, &'a str),
+    IsZeroLine(Register, LineNumber),
+    JumpLabel(&'a str),
+    JumpLine(LineNumber),
+    Label(&'a str),
+    Stop,
+    None,
+}
+
+#[derive(Debug)]
+struct ParseErr {
+    span: Span,
+    inner: ParseErrInner,
+}
+
+impl ParseErr {
+    fn new(span: Span, inner: ParseErrInner) -> Self {
+        Self { span, inner }
+    }
+}
+
+#[derive(Debug)]
+pub enum ParseErrInner {
+    OutOfBoundsLineRef(LineNumber),
+    LabelNotFound(String),
+    ParseIntErr(ParseIntError),
+    NoRegister,
+    NoLabelOrLine,
+    IllegalStmt(String),
+}
+
+type StdResult<T, E> = std::result::Result<T, E>;
+type Result<T> = StdResult<T, ParseErr>;
+
+impl std::fmt::Display for ParseErr {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "error on line '{}': ", self.span.line_number())?;
+        match &self.inner {
+            ParseErrInner::OutOfBoundsLineRef(referenced) => {
+                write!(f, "Referencing line '{}': out of bounds", referenced.0,)
+            }
+            ParseErrInner::LabelNotFound(label) => write!(f, "Label '{}' not found", label,),
+            ParseErrInner::ParseIntErr(err) => write!(f, "{}", err),
+            ParseErrInner::NoRegister => write!(f, "No register provided"),
+            ParseErrInner::NoLabelOrLine => write!(f, "No label or line provided"),
+            ParseErrInner::IllegalStmt(stmt) => write!(f, "Illegal statement: '{}'", stmt),
+        }?;
+        write!(f, ".")
+    }
+}
+
+fn resolve_line_number(
+    stmts: &[(IrStmt, Span)],
+    number: LineNumber,
+    span: Span,
+) -> Result<StmtIdx> {
+    match stmts
+        .iter()
+        .position(|(_, stmt_span)| stmt_span.line_number() == number.0)
+    {
+        Some(stmt_number) => Ok(StmtIdx(stmt_number)),
+        None => Err(ParseErr::new(
+            span,
+            ParseErrInner::OutOfBoundsLineRef(number),
+        )),
+    }
+}
+
+fn resolve_label(labels: &HashMap<&str, StmtIdx>, span: Span, label: &str) -> Result<StmtIdx> {
+    match labels.get(label) {
+        Some(line) => Ok(*line),
+        None => Err(ParseErr::new(
+            span,
+            ParseErrInner::LabelNotFound(label.to_owned()),
+        )),
+    }
+}
+
+pub fn parse(text: &str, file_name: String) -> StdResult<Code, String> {
+    let mut labels = HashMap::new();
+
+    let mut ir_statements = Vec::new();
+    let mut statement_number = StmtIdx(0);
+
+    let code_lines = text.lines().collect::<Vec<_>>();
+
+    for (line_index, line) in code_lines.iter().enumerate() {
+        let span = Span(line_index);
+        let result = parse_line(span, line);
+        match result {
+            Ok(IrStmt::Label(name)) => {
+                labels.insert(name, statement_number);
+            }
+            Ok(IrStmt::None) => {}
+            Ok(stmt) => {
+                statement_number.0 += 1;
+                ir_statements.push((stmt, span));
+            }
+            Err(err) => return Err(err.to_string()),
+        }
+    }
+
+    let statements: Result<Vec<_>> = ir_statements
+        .iter()
+        .filter(|stmt| !matches!(stmt, (IrStmt::None, _)))
+        .map(|(stmt, span)| match *stmt {
+            IrStmt::Inc(r) => Ok((Stmt::Inc(r), *span)),
+            IrStmt::Dec(r) => Ok((Stmt::Dec(r), *span)),
+            IrStmt::IsZeroLine(r, line_number) => Ok((
+                Stmt::IsZero(r, resolve_line_number(&ir_statements, line_number, *span)?),
+                *span,
+            )),
+            IrStmt::JumpLine(line_number) => Ok((
+                Stmt::Jump(resolve_line_number(&ir_statements, line_number, *span)?),
+                *span,
+            )),
+            IrStmt::IsZeroLabel(r, label) => Ok((
+                Stmt::IsZero(r, resolve_label(&labels, *span, label)?),
+                *span,
+            )),
+            IrStmt::JumpLabel(label) => {
+                Ok((Stmt::Jump(resolve_label(&labels, *span, label)?), *span))
+            }
+            IrStmt::Stop => Ok((Stmt::Stop, *span)),
+            IrStmt::Label(_) => unreachable!(),
+            IrStmt::None => unreachable!(),
+        })
+        .collect();
+
+    statements
+        .map(|vec| {
+            let (stmts, span) = vec.iter().cloned().unzip();
+            Code {
+                stmts,
+                span,
+                code_lines,
+                file_name,
+            }
+        })
+        .map_err(|err| err.to_string())
+}
+
+fn parse_line(span: Span, line: &str) -> Result<IrStmt> {
+    let no_label_or_line_number = || ParseErr::new(span, ParseErrInner::NoLabelOrLine);
+
+    let mut iter = line.split_whitespace();
+    let first = iter.next();
+    let first = match first {
+        Some(first) => first,
+        None => return Ok(IrStmt::None),
+    };
+
+    Ok(match first {
+        "INC" => {
+            let register = next_register(&mut iter, span)?;
+            IrStmt::Inc(register)
+        }
+        "DEC" => {
+            let register = next_register(&mut iter, span)?;
+            IrStmt::Dec(register)
+        }
+        "IS_ZERO" => {
+            let register = next_register(&mut iter, span)?;
+            let jump_target = iter.next().ok_or_else(no_label_or_line_number)?;
+            if let Ok(line_number) = jump_target.parse::<usize>() {
+                IrStmt::IsZeroLine(register, LineNumber(line_number))
+            } else {
+                IrStmt::IsZeroLabel(register, jump_target)
+            }
+        }
+        "JUMP" => {
+            let jump_target = iter.next().ok_or_else(no_label_or_line_number)?;
+            if let Ok(line_number) = jump_target.parse::<usize>() {
+                IrStmt::JumpLine(LineNumber(line_number))
+            } else {
+                IrStmt::JumpLabel(jump_target)
+            }
+        }
+        "STOP" => IrStmt::Stop,
+        stmt => {
+            if let Some(stripped) = stmt.strip_prefix('.') {
+                IrStmt::Label(stripped)
+            } else if stmt.starts_with('#') {
+                IrStmt::None
+            } else {
+                return Err(ParseErr::new(
+                    span,
+                    ParseErrInner::IllegalStmt(stmt.to_owned()),
+                ));
+            }
+        }
+    })
+}
+
+fn next_register<'a>(iter: &mut impl Iterator<Item = &'a str>, span: Span) -> Result<Register> {
+    iter.next()
+        .ok_or_else(|| ParseErr::new(span, ParseErrInner::NoRegister))?
+        .parse()
+        .map(|num| Register(num))
+        .map_err(|parse_err: ParseIntError| {
+            ParseErr::new(span, ParseErrInner::ParseIntErr(parse_err))
+        })
+}

src/run.rs

@@ -0,0 +1,336 @@
+use crate::parse;
+use crate::parse::{Code, LineNumber, Register, Span, Stmt, StmtIdx};
+use std::io::Write;
+use std::path::Path;
+
+#[derive(Debug, Clone)]
+struct Vm<'a> {
+    stmts: Vec<Stmt>,
+    span: Vec<Span>,
+    code_lines: Vec<&'a str>,
+    pc: StmtIdx,
+    registers: Vec<usize>,
+    breakpoints: Vec<StmtIdx>,
+    file_name: String,
+}
+
+#[derive(Debug, Copy, Clone)]
+enum VmState {
+    Run,
+    Break,
+    Stop,
+    OutOfBounds,
+}
+
+impl Vm<'_> {
+    fn step(&mut self) -> VmState {
+        let pc = self.pc;
+        match self.stmts.get(pc.0).cloned() {
+            Some(Stmt::Inc(r)) => self.registers[r.0] += 1,
+            Some(Stmt::Dec(r)) => self.registers[r.0] -= 1,
+            Some(Stmt::IsZero(r, index)) => {
+                if self.registers[r.0] == 0 {
+                    self.pc = StmtIdx(index.0 - 1);
+                }
+            }
+            Some(Stmt::Jump(index)) => self.pc = StmtIdx(index.0 - 1),
+            Some(Stmt::Stop) => return VmState::Stop,
+            None => return VmState::OutOfBounds,
+        }
+        self.pc.0 += 1;
+        if self.breakpoints.contains(&self.pc) {
+            VmState::Break
+        } else {
+            VmState::Run
+        }
+    }
+
+    fn run(&mut self, time_kind: VmRunKind) -> VmState {
+        let now = std::time::Instant::now();
+        loop {
+            if let state @ (VmState::Break | VmState::Stop | VmState::OutOfBounds) = self.step() {
+                if let VmRunKind::WithTime = time_kind {
+                    println!("Vm ran for {}ms.", now.elapsed().as_millis());
+                }
+                return state;
+            }
+        }
+    }
+
+    fn statement_at_span(&self, search_span: Span) -> Option<StmtIdx> {
+        self.span
+            .iter()
+            .position(|span| *span >= search_span)
+            .map(|idx| StmtIdx(idx))
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+enum VmRunKind {
+    WithTime,
+    WithoutTime,
+}
+
+#[derive(Debug, Copy, Clone)]
+enum VmInstruction {
+    Step,
+    Run(VmRunKind),
+    Break(StmtIdx),
+    Set(Register, usize),
+    Stop,
+}
+
+pub fn start(program_path: Option<String>) {
+    if let Some(path) = program_path {
+        read_and_run(&path);
+    }
+
+    loop {
+        match loading_input() {
+            LoadInstruction::Quit => return,
+            LoadInstruction::Load(path) => read_and_run(&path),
+        }
+    }
+}
+
+fn read_and_run(path: &str) {
+    let path = Path::new(path);
+
+    match std::fs::read_to_string(path) {
+        Ok(content) => match parse::parse(&content, filename(path)) {
+            Ok(stmts) => run(stmts),
+            Err(why) => eprintln!("{}", why),
+        },
+        Err(why) => eprintln!("error while reading file: {}.", why),
+    };
+}
+
+#[derive(Debug, Clone)]
+enum LoadInstruction {
+    Quit,
+    Load(String),
+}
+
+fn loading_input() -> LoadInstruction {
+    loop {
+        let input = get_input(None);
+        let mut iter = input.split_whitespace();
+        if let Some(str) = iter.next() {
+            match str {
+                "l" | "load" => match iter.next() {
+                    Some(path) => return LoadInstruction::Load(path.to_owned()),
+                    None => println!("error: No file path provided to load from."),
+                },
+                "h" | "help" => print_load_help(),
+                "q" | "quit" => return LoadInstruction::Quit,
+                cmd => println!("error: Unknown command: {}.", cmd),
+            }
+        }
+    }
+}
+
+fn filename(path: &Path) -> String {
+    path.file_stem().unwrap().to_str().unwrap().to_owned()
+}
+
+fn run(code: Code) {
+    println!("Loaded {}.", code.file_name);
+    let max_register_index = max_register(&code.stmts);
+    let mut vm = Vm {
+        stmts: code.stmts,
+        span: code.span,
+        code_lines: code.code_lines,
+        file_name: code.file_name,
+        pc: StmtIdx(0),
+        registers: vec![0; max_register_index + 1],
+        breakpoints: vec![],
+    };
+
+    loop {
+        match debug_input(&vm) {
+            VmInstruction::Stop => break,
+            VmInstruction::Run(time_kind) => match vm.run(time_kind) {
+                VmState::Stop => break,
+                VmState::OutOfBounds => {
+                    print_program(&vm);
+                    print_registers(&vm);
+                    eprintln!("error: Program ran out of bounds.");
+                    return;
+                }
+                VmState::Run => {
+                    unreachable!("internal error: Program still running after returning from run.")
+                }
+                _ => {}
+            },
+            VmInstruction::Step => match vm.step() {
+                VmState::Stop => break,
+                VmState::OutOfBounds => {
+                    print_program(&vm);
+                    print_registers(&vm);
+                    eprintln!("error: Program ran out of bounds.");
+                    return;
+                }
+                _ => {}
+            },
+            VmInstruction::Break(line) => {
+                let position = vm.breakpoints.iter().position(|point| *point == line);
+                match position {
+                    None => vm.breakpoints.push(line),
+                    Some(pos) => {
+                        vm.breakpoints.remove(pos);
+                    }
+                }
+            }
+            VmInstruction::Set(r, value) => vm.registers[r.0] = value,
+        }
+    }
+    println!("Execution finished.");
+}
+
+fn debug_input(vm: &Vm) -> VmInstruction {
+    loop {
+        let input = get_input(Some(&vm.file_name));
+        let mut iter = input.split_whitespace();
+        if let Some(str) = iter.next() {
+            match str {
+                "r" | "register" => print_registers(vm),
+                "p" | "program" => print_program(vm),
+                "h" | "?" | "help" => print_debug_help(),
+                "b" | "break" => match iter.next() {
+                    Some(line_number) => match line_number.parse::<usize>() {
+                        Ok(line_number) => {
+                            let stmt_pos =
+                                match vm.statement_at_span(LineNumber(line_number).span()) {
+                                    Some(pos) => pos,
+                                    None => {
+                                        println!(
+                                            "error: Line number '{}' out of bounds for length {}.",
+                                            line_number,
+                                            vm.code_lines.len()
+                                        );
+                                        continue;
+                                    }
+                                };
+                            return VmInstruction::Break(stmt_pos);
+                        }
+                        Err(_) => println!("error: Invalid argument provided."),
+                    },
+                    None => print_breakpoints(vm),
+                },
+                "set" => match parse_set_command(&mut iter) {
+                    Some((reg, value)) => return VmInstruction::Set(reg, value),
+                    None => println!("error: Invalid arguments provided."),
+                },
+                "c" | "continue" => {
+                    if let Some("time") = iter.next() {
+                        return VmInstruction::Run(VmRunKind::WithTime);
+                    }
+                    return VmInstruction::Run(VmRunKind::WithoutTime);
+                }
+                "s" | "step" => return VmInstruction::Step,
+                "q" | "quit" => return VmInstruction::Stop,
+                cmd => println!("error: Unknown command: {}.", cmd),
+            }
+        }
+    }
+}
+
+fn parse_set_command<'a>(iter: &mut impl Iterator<Item = &'a str>) -> Option<(Register, usize)> {
+    let reg = iter.next().and_then(|reg| reg.parse().ok())?;
+    let value = iter.next().and_then(|value| value.parse().ok())?;
+    Some((Register(reg), value))
+}
+
+fn max_register(stmts: &[Stmt]) -> usize {
+    stmts
+        .iter()
+        .map(|stmt| match stmt {
+            Stmt::Inc(r) => r.0,
+            Stmt::Dec(r) => r.0,
+            Stmt::IsZero(r, _) => r.0,
+            Stmt::Jump(_) => 0,
+            Stmt::Stop => 0,
+        })
+        .max()
+        .unwrap_or(0)
+}
+
+fn print_registers(vm: &Vm) {
+    println!("Registers:");
+    for (i, r) in vm.registers.iter().enumerate() {
+        println!("{: >4} : {}", i, r);
+    }
+}
+
+fn print_program(vm: &Vm) {
+    use std::cmp::min;
+
+    if let Some(span_pc) = vm.span.get(vm.pc.0) {
+        println!("Program:");
+
+        let lower = span_pc.0.saturating_sub(5);
+        let higher = min(vm.code_lines.len(), span_pc.0 + 6);
+
+        for line_index in lower..higher {
+            let code_line = vm.code_lines[line_index];
+            if line_index == span_pc.0 {
+                println!("> {}  {}", Span(line_index).line_number(), code_line);
+            } else {
+                println!("{}  {}", Span(line_index).line_number(), code_line);
+            }
+        }
+    } else {
+        println!("Reached the end of the program.");
+    }
+}
+
+fn print_breakpoints(vm: &Vm) {
+    println!(
+        "Breakpoints:
+    {}
+    ",
+        vm.breakpoints
+            .iter()
+            .map(|p| p.0.to_string())
+            .collect::<Vec<String>>()
+            .join(", ")
+    );
+}
+
+fn print_load_help() {
+    println!(
+        "List of commands and their aliases:
+
+    load (l) <filename> -- Load and run a program
+    quit (q) -- Quits the program
+    help (h, ?) -- Shows this help page
+    "
+    );
+}
+
+fn print_debug_help() {
+    println!(
+        "List of commands and their aliases:
+
+    step (s) -- Steps the program forward by one step
+    set <register> <value> -- Sets a register to a value
+    break <line> (b) -- Set a breakpoint to a line, use again to toggle
+    continue (c) (time) -- Run the program until the next breakpoint, add 'time' to display execution time
+    register (r) -- Shows the contents of the registers
+    program (p) -- Shows where the program currently is
+    quit (q) -- Stop execution of the current program
+    help (h, ?) -- Shows this help page
+    "
+    );
+}
+
+fn get_input(prompt: Option<&str>) -> String {
+    let mut input_buf = String::new();
+    match prompt {
+        None => print!("(m8db) "),
+        Some(text) => print!("(m8db - {}) ", text),
+    }
+    std::io::stdout().flush().unwrap();
+    std::io::stdin().read_line(&mut input_buf).unwrap();
+    input_buf.trim().to_owned()
+}

src/stmt.rs

@@ -1,80 +0,0 @@
-use std::fmt::Formatter;
-use std::num::ParseIntError;
-
-#[derive(Debug, Copy, Clone)]
-pub enum Stmt {
-    Inc(usize),
-    Dec(usize),
-    IsZero(usize, usize),
-    Jump(usize),
-    Stop,
-}
-
-pub fn parse(text: &str) -> Result<Vec<Stmt>, String> {
-    text.lines().map(parse_line).collect()
-}
-
-fn parse_line(line: &str) -> Result<Stmt, String> {
-    const NO_REGISTER: fn() -> String = || "No register".to_string();
-    const NO_LINE_NUMBER: fn() -> String = || "No line number".to_string();
-    const EMPTY_LINE: fn() -> String = || "Empty line not allowed".to_string();
-    const DISPLAY_ERR: fn(ParseIntError) -> String = |parse_err| parse_err.to_string();
-
-    let mut iter = line.split_ascii_whitespace();
-    let first = iter.next().ok_or_else(EMPTY_LINE)?;
-
-    Ok(match first {
-        "INC" => {
-            let register = iter
-                .next()
-                .ok_or_else(NO_REGISTER)?
-                .parse()
-                .map_err(DISPLAY_ERR)?;
-            Stmt::Inc(register)
-        }
-        "DEC" => {
-            let register = iter
-                .next()
-                .ok_or_else(NO_REGISTER)?
-                .parse()
-                .map_err(DISPLAY_ERR)?;
-            Stmt::Dec(register)
-        }
-        "IS_ZERO" => {
-            let register = iter
-                .next()
-                .ok_or_else(NO_REGISTER)?
-                .parse()
-                .map_err(DISPLAY_ERR)?;
-            let line_number = iter
-                .next()
-                .ok_or_else(NO_LINE_NUMBER)?
-                .parse()
-                .map_err(DISPLAY_ERR)?;
-            Stmt::IsZero(register, line_number)
-        }
-        "JUMP" => {
-            let line_number = iter
-                .next()
-                .ok_or_else(NO_LINE_NUMBER)?
-                .parse()
-                .map_err(DISPLAY_ERR)?;
-            Stmt::Jump(line_number)
-        }
-        "STOP" => Stmt::Stop,
-        stmt => return Err(format!("Illegal instruction: '{}'", stmt)),
-    })
-}
-
-impl std::fmt::Display for Stmt {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Stmt::Inc(r) => write!(f, "INC {}", r)?,
-            Stmt::Dec(r) => write!(f, "DEC {}", r)?,
-            Stmt::IsZero(r, line) => write!(f, "IS_ZERO {} {}", r, line)?,
-            Stmt::Jump(r) => write!(f, "JUMP {}", r)?,
-            Stmt::Stop => write!(f, "STOP")?,
-        }
-        Ok(())
-    }
-}

test.m8

@@ -1,5 +1,7 @@
-IS_ZERO 1 5
+INC 1
+JUMP 7
+INC 2
+STOP
 INC 3
-DEC 1
-JUMP 1
-STOP
+
+JUMP 4